linux-kernel - [PATCH net] ipv6: fix panic when forwarding a pkt with no in6 dev

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Date:   Fri,  8 Apr 2022 16:03:42 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        kongweibin <kongweibin2@...wei.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Vasily Averin <vvs@...tuozzo.com>,
        Martin KaFai Lau <kafai@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, rose.chen@...wei.com,
        liaichun@...wei.com, Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        stable@...r.kernel.org
Subject: [PATCH net] ipv6: fix panic when forwarding a pkt with no in6 dev

kongweibin reported a kernel panic in ip6_forward() when input interface
has no in6 dev associated.

The following tc commands were used to reproduce this panic:
tc qdisc del dev vxlan100 root
tc qdisc add dev vxlan100 root netem corrupt 5%

CC: stable@...r.kernel.org
Fixes: ccd27f05ae7b ("ipv6: fix 'disable_policy' for fwd packets")
Reported-by: kongweibin <kongweibin2@...wei.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com>
---

kongweibin, could you test this patch with your setup?

Thanks,
Nicolas

 net/ipv6/ip6_output.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index e23f058166af..fa63ef2bd99c 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -485,7 +485,7 @@ int ip6_forward(struct sk_buff *skb)
 		goto drop;
 
 	if (!net->ipv6.devconf_all->disable_policy &&
-	    !idev->cnf.disable_policy &&
+	    (!idev || !idev->cnf.disable_policy) &&
 	    !xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {
 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 		goto drop;
-- 
2.33.0